Radiohead frontman Thom Yorke is no tourist in the climate activism world — he’s defended fair trade, campaigned for Friends of the Earth, edited a climate change edition of the Observer, and sought to make Radiohead’s tours low carbon affairs. And now he’s come to Copenhagen, just hours before a possible agreement, determined to find reason for optimism — and perhaps set world leaders straight.

I spoke to the head Radiohead yesterday, shortly after he emerged from a meeting with the UK environment minister Ed Milliband, looking as harried and caveman-like than ever.